French Onion Soup Crostini – Gooey Caramelized Onion Appetizer
If you love French onion soup but want something a little more party-friendly, these French Onion Soup Crostini are calling your name. Caramelized onions, a hint of red wine, and melted truffle Gouda on crispy crostini make an irresistible appetizer that’s perfect for entertaining—or sneaky snacking when no one’s looking.
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If you didn’t already know (or if you’re new here!), I have a major love for French onion soup. Naturally, I had to create a crostini version! This recipe came to life during a Cheeselandia party, and the moment I opened the box and spotted the Marieke® Truffle Gouda, I knew exactly where we were headed. 🧀✨
These French Onion Soup Crostini are rich, savory, ever-so-slightly sweet, and topped with gooey melted truffle Gouda over deeply caramelized onions. Crisp, elegant, and wildly comforting, they’re perfect for entertaining—or simply treating yourself because, honestly, you deserve it.
Why You’ll Love This Recipe
Ingredients Notes:
This recipe is rich in layers of flavor by using traditional French cooking techniques. Adding each ingredient slowly takes some time, but it is well worth the effort. Below are some notes on the ingredients and substitution suggestions.
Onions:
White onions have a lighter onion flavor and cook down faster. This gives that signature French onion soup flavor without an extra long simmer.
Red wine:
Adds depth and richness. Avoiding alcohol? Replace it with extra beef (or vegetable) broth.
Cheese:
Truffle Gouda is luxurious, but plain Gouda is a perfectly delicious substitute.
Sugar:
Brown sugar adds warmth and caramel notes; white sugar works if you’re in a pinch.
Herbs de Provence:
Becoming more readily available, you should be able to find it in most spice aisles. But if you can’t or if you’re out, no worries! Dried thyme (1:1 ratio) does the job.
Dietary Details
This appetizer is incredibly easy to adapt for multiple diets:
- Vegetarian: Swap beef broth for vegetable broth.
- Vegan: Use vegetable broth, replace the Gouda with vegan mozzarella, and substitute butter with olive oil.
- Gluten-Free: Use cornstarch or tapioca starch instead of flour, and reach for a gluten-free baguette for your crostini.
Small swaps make this recipe welcoming, inclusive, and just as delicious for your next appetizer or party hors d’oeuvres.
Cooking with Kids
Yes, there’s stovetop cooking and baking involved—but there’s still plenty of room for little helpers.
Storage
These crostini are meant to be eaten immediately, but if you have a couple left over, store them in a food-safe container and consume within 2 days.
- Store the onion topping in a food-safe bag for up to 5 days.
- Keep the onions, cheese, and crostini separate until you’re ready to serve.
- To reheat: top crostini with onions and cheese and bake at 350°F until the cheese melts and everything warms through.
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French Onion Soup Crostini
- Total Time: 50 minutes
- Yield: 12 crostini 1x
Description
These French Onion Soup Crostini are bite-sized perfection—caramelized onions, a touch of red wine, and gooey truffle Gouda on crisp crostini. Perfect for parties, appetizer spreads, or an indulgent snack, they bring all the rich, savory flavor of classic French onion soup into a fun, handheld version.
Ingredients
- 12 crostini [see notes for dietary substitutions]
- 1/4 lb Truffle Gouda, cut into 12 slices [see notes for substitutions]
- 1 large or 2 small white onions, halved and thinly sliced [see notes for substitutions]
- 2 Tbsp unsalted butter [see notes for dietary substitutions]
- 1/2 cup beef broth [see notes for dietary substitutions]
- 1/2 cup dry red wine (or extra broth) [see notes for substitutions]
- 1/2 Tbsp flour [see notes for dietary substitutions]
- 1/2 tsp brown sugar [see notes for substitutions]
- 1/2 tsp Worcestershire sauce
- 1/2 tsp Herbs de Provence [see notes for substitutions]
- 1/4 tsp salt
Instructions
-
Melt butter in a large skillet over medium heat. Add onions and cook for 5 minutes, stirring constantly. Reduce to medium-low and cook 10–15 minutes until golden brown, stirring occasionally.
-
Add brown sugar and red wine. Cook, stirring, until wine evaporates and onions look deep and glossy (~10–15 minutes).
-
Stir in flour, Herbs de Provence, and salt until onions are fully coated.
-
Slowly add broth, stirring continuously. Add Worcestershire sauce. Bring to a boil over medium-high, then reduce to medium and cook 7–8 minutes, until most liquid evaporates.
-
Arrange crostini on a baking sheet. Top with onion mixture and Gouda slices. Bake at 350°F for 6–8 minutes, until cheese is melted and bubbly.
Notes
Substitutions:
- Onions: White onions cook faster, but yellow onions can also be used (1:1 ratio).
- Red wine: Can be replaced with extra broth for alcohol-free version (1:1 ratio).
- Cheese: Truffle Gouda can be substituted with plain Gouda(1:1 ratio).
- Brown sugar: White sugar works in a pinch (1:1 ratio).
- Herbs de Provence: Can substitute 1:1 with dried thyme.
Dietary Details and Substitutions
To make it Vegetarian:
- Broth: Beef broth can be replaced with vegetable broth to make this fully vegetarian.
to make it Vegan:
- Cheese: Truffle Gouda can be substituted with a vegan mozzarella (1:1 ratio).
- Broth: Beef broth can be replaced with vegetable broth, in a 1:1 ratio,to make this fully vegetarian.
to make it Gluten free:
- All-Purpose Flour: Use cornstarch or tapioca starch instead of flour (1:1 ratio)
- Crostini: Use a Gluten free baguette to make the crostini instead of a traditional baguette.
- Prep Time: 15 minutes
- Cook Time: 35 minutes
- Category: Appetizer/hor d’oerves
- Method: Stove + Oven
- Cuisine: French
©Photo, Prop Styling, and Food Styling by Jenn Smith
©2025 Cheers, Jenn™ | Cheers, Jenn Smith™ | Jenn Smith, LLC (FKA Smith Country, LLC)
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